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//二分查找法--递归实现class Rank{ public static void main(String[] args){ int[] arr = {0,10,8,9,111}; System.out.println(rank(8,arr)); } public static int rank(int key , int[] a){...

题：求1+2+3+4+5+…+n的和递归代码public int sum(int n){ if(n==1){ return 1; }else{ return n+sum(n-1); } }while public int sum(int n){ int su...